Intrastromal Surgery Correcting Low Order and High Order Aberrations

Abstract

A method of correcting wavefront aberrations of an eye includes determining a high precision conventional intrastromal corneal ablation profile based on a direct removal of the intrastromal corneal tissue. An expanded ablation volume profile is constructed based on the direct tissue removal profile and the expanded tissue volume is to be ablated instead to correct to the wavefront aberrations. The thickness of the ablated profile of a conventional ablation profile is expanded by an expansion factor (Nc-1) / (Nm-Nc), Nc is the index of refraction of the cornea and Nm the index of fill material. An expanded ablation volume filled with the fill material produces the effect of correcting wavefront aberrations as if a much smaller tissue volume were ablated without the fill material.

Description

PRIORITY [0001] This application claims the benefit of priority to U.S. provisional patent application No. 60 / 820,483, filed Jul. 26, 2006, which is hereby incorporated by reference.BACKGROUND [0002] Currently refractive errors are routinely corrected with a laser surgical procedure LASIK or PRK. Laser energy is applied to the front surface of the eye in PRK, or to the stromal surface after a thin corneal flap is resected and pulled back in LASIK. Both procedures have disadvantages. In PRK, it is painful and the healing time is long. In LASIK, it is less painful. However, the corneal flap being cut weakens the mechanical structure of the eye. Reported cases of post-LASIK ectasia have begun to cause concerns and serious discussions regarding its prevention have sprung up at recent ophthalmology meetings. The focus of the discussions is on patient selection, and when to avoid operating on patients with “risk factors”. [0003] Therefore, it is desirable to provide a surgical correction ...

AI Technical Summary

Benefits of technology

[0014] The ablation planes may be ordered starting from the farthest to the closest plane to the anterior cornea surface. The laser may be directed to ablate tissue in accordance with the farthest ablation plane. The tissue ablation process is continued to the next ablation plane in the sequence, and repeated until the tissue volume is dissected in accordance with the cut pattern. The calculating may include overlapping focused laser pulses between 0.7 to 1.8 of the laser spot radius within the region of tissue to be dissected. Volumes of corneal tissue between lines of the grids of the adjacent layers are advantageously removed even though they are not directly ablated, thereby reducing heating of the cornea compared with a process of direct ablation of the entire removed corneal tissue volume.

Problems solved by technology

In PRK, it is painful and the healing time is long.

However, the corneal flap being cut weakens the mechanical structure of the eye.

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